Two stage electrohydraulic pressure control valves are commonly used for actuating clutches or brakes where the output pressure is generally proportional to an electrical signal. Any of the current control valves have a pilot stage for providing a regulated pressure at a low flow rate for controlling a larger main stage that handles the main flow to and from the brakes or clutches. Some of the pilot stages function by controlling fluid flow through a bleed path from the main fluid supply to a tank to generate the regulated pressure at an end of the main stage valve spool. A continuous bleed flow exist even when the control valve in at its closed position. The bleed flow rate through the bleed path is generally very low and does not adversely affect the performance of the clutch or brake system. However, the continuous bleeding of fluid is detrimental to a braking or clutch system which uses an accumulator as a secondary or backup source since the accumulator is quickly depleted even when the control valves are not being actuated.
Thus, it would be beneficial to provide a two stage electrohydraulic control valve which has fluid flowing through a pilot stage flow path flow only when the control valve is actuated and flow through the flow path is positively blocked when the control valve is in its flow blocking position.
The present invention is directed to overcoming one or more of the problems set forth above.